[Rtk-users] Parker weighting

[Simon Rit]

Hi,
rtkfdk.cxx just read the geometry from a file so the best is to modify the
geometry file. How do you generate the geometry?
For example, if you use rtksimulated geometry, let's say that you were
using:
rtksimulatedgeometry -n 200 -a 200 -o g.xml
then you'll have to replace it with
rtksimulatedgeometry -n 202 -a 202 -o g.xml -f -1
Don't forget to add dummy projection at the beginning and the end. If you
use a more complex geometry, maybe SimpleRTK
<http://wiki.openrtk.org/index.php?title=SimpleRTK> can be helpful (I'd use
that) or you'd have to modify the cxx code to add these additional
projections in the geometry and the projection stack.
Simon


On Tue, Dec 8, 2015 at 8:51 AM, Shiras Abdurahman <shiraska at gmail.com>
wrote:

> Dear Simon,
>
> Thanks a lot for the reply. Can you please inform me how can I set where
> the arc starts?
> Do I need to modify geometry also?
> If you can point the line of code rtkfdk.cxx, it will be really helpful.
>
> With regards,
> Shiras
>
> On Tue, Dec 8, 2015 at 7:56 AM, Simon Rit <simon.rit at creatis.insa-lyon.fr>
> wrote:
>
>> Dear Shiras,
>> Yes, for practical reasons the first and the last projections are set to
>> 0 and the arc used in the Parker weighting starts between the first two
>> projections and ends between the lasts two projections. There is a simple
>> solution: add a projection at the beginning and the end of the arc, which
>> can contain any pixel values but should be set where you want this arc to
>> start. In the future, I think someone should once take the time to correct
>> this but I haven't so far. I'll keep you posted on the mailing list when
>> it's corrected.
>> Simon
>>
>> On 07/12/2015 12:04, Shiras Abdurahman wrote:
>>
>> Hi all,
>>
>> I am trying to reconstruct a volume from projection data generated with
>> C-arm CT. There are 248 projections with an angular range of 199 degree.
>> Technically, parker weighting should run without any problems. However, I
>> am getting an output message that "You do not have enough data for proper
>> parker weighting". After parker weighting, the two extreme projections
>> (projection number 1 and 248) were completely zero and thus reconstructed
>> volume contained artifacts. When I increased the angular range, this
>> problem did not happen. How can I solve this problem without increasing
>> angular range? Is there any threshold constant that I can change in command
>> line  or in my code?
>>
>> I really appreciate any help you can provide.
>>
>> With regards,
>> Shiras
>>
>>
>> _______________________________________________
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>>
>>
>>
>
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